Abstract：An ecological security index (ESI) system of Lake Dongting was constructed with 14 indices, according to the driving force-pressure-state-impact-risk model. The weights of the indices were determined by analytical hierarchy process (AHP), and the ecological security status classification was evaluated by the ESI model for the years of 2000, 2005 and 2007. The ecological security was ranked as the safe grade in 2000 and the general grade in 2007, indicating a decrease in ecological security. In 2007, compared to the benchmark, the status score was only 57.2%. With further analysis, the TP and Chl.a were the main reason for the water deterioration of the Lake Dongting.
